Flotation process



0a. 7, 1941. E H, HOAG 2,258,507

FLOTATION PROCESS Filed Aug. 27, 1940 3 Sheets-Sheet l gi w 45 1 4,

' INVENTOE 1?. fbm ARDH. hoAav A TropA/EK Oct. 7, 1941. I H, HOA2,258,507

FLOTA' I'ION PROCESS Filed Aug; 2'7, 1940 3 Sheets-Sheet 2 INVENTOEEDWARD H. HOAC f1 TTORNEY v Patented Oct. 7, 1941 This invention relatestothe separationby mechanical, physical andichemical means of thevaluable gconstituents of 'rocks, ores; minerals and chemical productsbased primarily'on the f difference in'flotativeproperties'oi thecontentdue to. a combination" '01" acts by'which a deli-'3- nite anddeslrablegelectrical sign and chargeis' face of saidmineralsjorproducts. g I

An important object of :the invention is *to -.Umjgo fj tsirnrEs PATENTOFFICE accomplished by means of the process described herein andillustrated in the accompanying drawings, in which:

[ Fig. 1 is a plan view of the apparatus, partly broken away and partlyin. section. Fig. 2 is a central vertical section of the ap paratustaken on line 2--2 of Fig. 1 looking in formed, or a modification ,ofsame, on the suri accelerate the time necessary to cause-minerals. v

to rise to the surface of pulp in the form of flotation froth andcollect-there as such their respective classes and kinds.

Another important object is to provide a proc ess that will activate ordepress desirable or uninto I the direction indicated by the arrowstherein.

' Fig. is a cross section of the apparatus takenonthe line 3-3 of Fig. 2looking in the directionindicated by the arrows-thereon.

-Fig. 4 is-anend elevation of the apparatus.

Fig. 5 is a longitudinal section view of the ionizationapparatus. I Fig.6 is an electrical diagram of the circuit of the-ionization apparatus.

desirable minerals in a flotation bath and separate them from each otherby modifying' the electrical sign and charge on the surface of saidminerals. 1

Another object is to provide a flotation proc-, ess in which theflotation bath is ionized by introducing therein direct current impulsesto completely immersed electrodes interrupted for short intervals.

A further object is to cause an attraction of basic oxides, colloidalbasic hydroxides and magnetizable minerals towards negative electrodesimmersed in a flotation bath, to remove said minerals from the bath andto impede adsorption of colloidal basic hydroxides and hydrolysedsilica.

A further object is to attract negative and positive suspensoids towardspositive and negative electrodes respectively.

A further object is to impede film-forming minerals from depressingdesirable minerals in the presence of activating reagents.

A further object is to focculate colloidal mineral suspensions andprevent undesirable films from forming on desirable minerals.

A further object is to provide a new method for differential separationof minerals into commercial products.

A further object is to utilize the ions formed in -a flotation bath orthe ions released from reagents and conditioners by the introductioninto said bath of direct current impulses interrupted for shortintervals.

Further-objects will hereinafter appear are 1 Fig.-7 is an enlargeddetail of the central portion of the agitation chamber of the apparatusillustrating the movement of the pulp during the operation of theapparatus.

8 is-a diagram of the electrical circuit 'j-ior introducing into aflotation bath direct ourany well known interrupter 31. 25

rent impulses interrupted for short intervals by Fig; 9 is an enlargedsectional plan in more detail of one of the air distributing pipes andadjacent. electrodes connected in circuit with a source of electricalenergy, showing direct current impulses introduced to electrodescompletely immersed in a flotation bath In, said currents interruptedfor short intervals by the mechanical interrupter 31 used for breakingsaid circuits.

In the appended drawings I have illustrated an apparatus by means ofwhich my improved process may be practiced eflicien'tly.

In the drawings, It indicates the cell or tank of the apparatus, havingupwardly and outwardly inclined side walls H and vertical end walls I2.

Centrally disposed and extending longitudinally of the cell I0 is acentrally disposed trough l3 through which the sands or heavy particlespass, and serves to bring the pulp into intimate contact with theimpellers l4 mounted therein.

These impellers are of the usual form and are secured to the lower endsof hollow vertical shafts l5, their upper ends being provided withpulleys l8 belted to a suitablev source of power as an electric motor 28to' operate the impellers,

air from a suitable source of power passing through the hollow shafts |5into the pulp. The pulp is fed to the trough II through a conduit |lwhere it is uniformly distributed by the impellers.

Arranged in the tank and on each side of the impellers are verticallyextending partitionsby valves 25 by means of which the froth may beenriched during its agitation.

The rear wall of the tank I0 is provided with an opening 25 controlledby a weir gate 21 for regulating the level of the pulp in the tank.

Mounted one side of the tank l0 and preferably at its top portion is adriving motor 28 for operating the various devices employed in theapparatus'as will be more fully set forth hereinafter.

Disposed on one of the top corners of the tank is a small electricgenerator M for generating direct current impulses for delivery to thepulp through the various electrodes disposed in the tank. Mounted on oneof the upper corners of the tank and opposite to the generator M is apressure blower 29 connected to an enlarged elecan alternating currentgenerator M'- standard make that delivers an initial current trical airchamber 30 that leads to an ionization V apparatus 3| which will bedescribed with greater particularity hereinafter. The ionized air fromapparatus 3| passes through a pipe line 32 to the various perforatedpipes disposed in the chambers of the apparatus.

In addition to the ionizing apparatus duclng and injecting ions into themineral pulp, an electrical apparatus is employed which preferablyconsists of a plurality of electrodes 33 disposed in the variouschambers of the apparatus.

These electrodes are arranged in positive and negative pairs, a pair toeach chamber, their ends being secured in the end walls of the tank andinsulated therefrom. These electrodes are preferably disposed atconvenient heights near the perforated air pipes 24 and are completelyimmersed in the flotation'bath.

The various pairs of electrodes are connected in circuit with thepositive and negative terminals 34 and 35 of the generator M, aninterrupter 31 of well-known type being interposed in the electricalcircuit to break the direct current impulses for intervals of not lessthan one second.

The impellers, as well as all other operable mechanisms are actuatedfrom the driving motor 28 through the agency of belts and pulleys in theusual well known manner.

Tailings are discharged through the opening 33 into launder 40, and fora very large capacity through 38:: also, while the froth bearing theval-. uable concentrates overflows into the launders 4| secured to theside walls of the apparatus, the overflow lips being adjustable tocontrol the how of froth thereto. 1 I

The enlarged detail of the lower portion ofv the tank as shown in Fig. 7is to illustrate the passage of the pulp through the apparatus duringbeneflciation. Secured directly above the centrally disposed partition20' and spaced therefrom to for pro-.

form a passageway between designed to control the retention of froth ineach tank section and the flow of pulp from the exit toward the head inthe agitation chamber of the apparatus during its treatment.

Pipe line 30a leading from the air pressure chamber 30 shown in Fig. 2,directs concentrates which overflow from section B of the tank tolaunder 4| and to a and how they may be returned to tank section A by asuitable air lift apparatus which includes 300 under low air pressure toenrich the lower grade concentrates from tank section B if suchprocedure is essential.

The source of current for operating the electrical elements mountedtherein is delivered from of any varying from to 440 volts, and thiscurrent can be stepped up to greater voltages, that is, from 5000 to35,000 volts by means of the transformer 50 mounted in one end of thecasing controlled by a rheostat 5|, a rectifier R. and a pair of two-wayswitches a and a located on the switchboard.

In the drawings only a single electrode has been shown, but it isobvious that several may be employed depending upon the ionizationrequired in the beneficiation of different classes of ores.

The electrode 55 here illustrated preferably consists of a central rod56 formed of aluminum, its upper and lower ends passing through circularplugs 51, 58 formed of glass cement and secured to insulated plates 59and 50 disposed within the ionization apparatus casing. Engaging theplugs 51 and 58 is a cylindrical glasstube 6|, containing an intimatemixture of aluminum filings and carbon grains 52 tightly packed therein.Surrounding tube GI and spaced therefrom as at 63 is an aluminumcylinder 64 provided with a plurality of perforations 65 for the releaseof ions formed by the electrode on their passage through the corona.

The operation of the ionization apparatus is as follows: The electricalcurrent from the generator flows through a rheostat 5 I, from thence itis led to the primary winding of a transformer 50 by line wires '10 andII. From the secondary windings 52 of the transformer it is conducted byline wires 53 and 54 to a synchronous rectifier R through line wires 53'and 54' to a pair of twoway switches a. and a. Negative ions are createdand discharged through the perforated cylinder 64 of the electrode 55 byconducting the electrical current from transformer 50 through line wire53 to synchronous rectifier B through line wire 53' and too and thencethrough line wire 8| to electrode 55. Line wire 54 leads to synchronousrectifier R and through line wire 54 to switch a through line wire 82 toperforated cylinder 64.

Positive ions are created in and discharged from cylinder 54 of theelectrode 55 by connecting the current from transformer 50 through linewire 54 to synchronous rectifier R. and through I line 54' to switch athrough line wire 1'! and switch a through line wire 8| to electrode 55.

the tank section A r and B is a transversely disposed partition 20a*tionbath of known hydrogen ionconcentration electrodes contained:-

the newer direct current impulses has been. 'oil-g'lobuleentity: y

intervals ofhotiessthan ine sleconcl'. obiec p. bath-is alkaline fthenthe-foil -filmwould take a tive being-tormodi-fyqori-changethe;gelect'rical.-5l.negatiye sign nlt is obvious then, ithatLany sign.and charge on .the surface oi min'erals; allowsome of" the reagents orconditioners... return to theiroriginal status. and structure after; a

interrupted for short intervals; to accelerate the Flotationlf agentswhen introduced into La v n r lithe hydrogen ioi'rcoricen fora ventempeetnre tocomhletelgimmersed' tra'tion-ofthebath.isacid'then the film onthe herein};-interrtiptcdiktor-;-,-air-oil-globule"takes;azpositivelsign, ,and it the 7 change ormodificationvinthe pH-value of -the fl I d n .change or modification ptta-17.1 1 Ele trical sign :finthcfoil film of the airdissociationofmolecules of reagents and condi, flotation bath generally. consist otmolecules'of, tioners as'well as torurnish' desirable additional theunsaturated type witltiree valences which in ions to the bath forcollectingor for conditioning turn. partly explains why they have suchan 1 purposes; to attract negative andpositive mineral intenseattraction for minerals and also-f for-the l. j suspensoids towards thepositive-and. negative rapid exchange of their free ions withsaidj'r'nin- 1 electrodes respectively; and finally, to modify the eralsto form the insoluble film on their surfaces hydrogen ion concentrationof the flotation bath. by adsorption.

Introducing flotation reagents with the object Y Polarmolccules such asCHO, COOH, and OH of forming an insoluble film onthe surface of typeschange emulsoids to suspensoids by removal minerals and to give saidminerals-and-fllms a 20 'of the water film from .the emulsions.desirable electrical sign and charge. An electrical charg'e'introducedinto a flota- Introducing conditioners for the purpose of tion bathwhich is opposite and equivalent to modifying the electrical sign andcharge on the the charge and sign'on the mineral and fllm will surfaceof minerals as well as for modifying the neutralize it. This phenomenapartly explains pH value of the pulp. how minerals can be depressed orprecipitated;

Introducing ionized air to furnish positive or how the pH value of theflotation bath is modified, negative ions from the air for theair-oil-globule how minerals and reagents or negative or positive entityand for the mineral-and-fllm entity so as colloids and minerals of theopposite sign and to have the desirable electrical sign and chargecharge are restrained from exchanging ions freely desirable forflotation of minerals. with each other.

The introduction of direct current impulses -Flocculati0n is antecedentto flotation of into the flotation bath to the immersed electrodesminerals and the first step or importance before contained therein is astep which modifies or the physics-of wetting. changes the electricalsign and charge on the The stability of mineral suspensions represurfaceof colloidal basic hydroxides, minerals 3. sented by the magnitude ofthe electrical charge in suspensions and film-forming minerals, and andsign on their surface is modified by introalso serves to attract saidminerals towards said ducing direct current impulses into a fotationelectrodes until-released by the interruption of bath interrupted forshort intervals, together with the direct current impulses for shortintervals. electrolytes, reagents and conditioners which give If saidminerals are neutralized then their original 40 off ions of the oppositesign and charge to that electrical sign is changed or modified andthereof the minerals and solution. When minerals fore they do notexchange ions with other are suspended in a liquid medium I findnegative minerals or with reagents or chemicals in the reagents givingoff large negative ions to negative same manner or intensity, as they dobefore the minerals to increase their stability; and to positiveintroductionof the flow of direct current impulses. minerals to decreasetheir stability; and I also Any change or modification of the hydrogenion find, that positive reagents give large positive ions concentrationof the flotation bath definitely to increase the stability of positiveminerals and changes or modifies the electrical sign and charge todecrease the stability of negative minerals.

on the surface of minerals. If the pH value of Nega ive 0 a o c reagentsv Off heavy the bath increases to a higher order of acidity negativeions presumably reacting on minerals or alkalinity then stabilizationincreases also to suspended in a solution W n ss cia ed y a certaindegree. Some minerals adsorb others direct current impulses inte ptedfor short more intensely so it is obvious that different intervals as +Hand O ions 10 in e p e e minerals in the same flotation bath aremodified of water, that is, they increase the negative and differentlyby any change or modification of the decrease the positive charge ofelectricity on the hydrogen ion concentration of the flotation bath. urce o m era s; 01 they decrease the P Some minerals can 'be destabilizedduring the value or increase the acidity or decrease the interruption ofdirect current'impulses or while alkalinity of 1 the solution; or theyincrease the they approach the isoelectric point. Minerals stability ofne er s and decrease the may be flocculated, depressed or precipitatedby so stability of P i ve miner ls; or they increase introducing into aflotation bath direct current flocculation of positive minerals anddecrease impulses interrupted for short intervals when flOcc atio of native minerals.

the electrical charge and sign are equal and Positive or cationicreagents under the above opposite t that f the minerals, v conditionsgive off heavy positive ions decreasing Minerals in the depressed statesubmerge and the negative charge and increasing the positive join ganguematerials in their exit from the charge of electricity on the surface ofminerals;

bath or they increase the pH value or decrease the The interruption ofdirect current impulses acidity or increase the alkalinity of theflotation allows some reagents and conditioners to return bath; or theydecrease the stability of negative I to their original structure andstatus and to or increase the stability of positive minerals; or

serve again in their original capacity for actlvatthey decreaseflocculation of positive or increase ing and depressing minerals.flocculation of negative minerals.

When frothing oils are introduced into a flota- The pH value of aflotation bath is changed or tion bath a film of oil is formed on theair-oilmodified by introducing direct current impulses globules takirm adefinite electrical sign from to electrodes immersed therein andinterrupted for short intervals if said bath contains reagents orconditioners, by accelerating the dissociation of its molecules or bysupplying desirable additionalions which are introduced therein. Thatis, negative reagents and conditioners will give charged electricallydue to grinding operations in a .mill,'and finally, oxides of the abovemetals formed by nature.

oif negative ions and the pH value of the solution will decrease or itsacidity will increase while positive reagents and conditioners will giveoff positive ions and the pH value of the solution will increase or itsalkalinityincreases.

In view of the'above the process is subordinate.

to changes or modifications of the sign and The tails consist ofsiliceous materials, calcite,

' aluminum compounds, oxides, positive and negative colloids, oxides ofiron, alumina and some of the valuable constituents in the ore assuscharge on the surface of minerals caused by introducing directcurrent impulses to a flotation bath to completely immersed electrodescontained therein and then interrupting the impulses for short intervalsof not less than one second as referred to heretofore in combinationwith the other steps in the process, by which minerals are activated ordepressed and the pH value of the pulp solution modified accordingly.

pensoids, clays, micas, together with small amounts of sulfides of themetallic content and rusty gold. 1

The processconsists of a series of actsby which materials aretransformed into a new state, that is, physically due to the changes ormodifications of their electrical charge and sign on the surface ofminerals, or chemically by metathetical exchanges between molecules orby adsorption, and said acts are related to each other and necessary forthe improved flotation of minerals.

The process is also subordinate to the modifled sign and charge on thesurface of minerals a flotation bath in order that said minerals cannotexchange their ions freely with undesirable minerals to activate them.For example, if a flotation bath contains colloidalbasic hydroxides assuspensoids they will exchange ions freely with hydrolysed silica inthepresence of positive concaused by removing film-forming minerals fromThe procedure topractice the invention for the above orev is as follows:1

First introduce into a flotation bath direct current impulses of 220volts and 1.5 amperes to completely immersed electrodes containedtherein for approximately 3 seconds. The impulses are interrupted forintervals of 3 seconds by a mechanical interruptor which breaks thecurrent for desirable intervals.

ditioners and negative reagents in an alkaline of not less than onesecond in combination with the other steps in the process, assists inprecipitating, neutralizing, flocculating or destabilizing minerals whenthey are in a fine state of suspension by restraining them fromdepressing desirable minerals in said path, that is, if the electricalcharge and sign is equivalent and opposite to the charge and sign on themineral.

When minerals are in a fine state of-suspension or in a colloidalcondition in' a flotation bath, they are known to be electricallycharged with a positive or negative sign. Such minerals, that areattracted towards positive electrodes during the flow of direct currentimpulses are classed as negative minerals and a few of them included inthis class which are found in the following example to illustrate theprocess are gold, silver, arsenious sulfides, cupric sulfide, sulfidesof iron, antimony, arsenic, lead and copper. Minerals in suspensionwhich are attracted towards the negative electrodes during the flow ofdirect current impulses are classed as positive minerals Secondly, thehydrogen ion concentration of the flotation bath is determined in termsof acidity or alkalinity for a given temperature such as the systemtaught by La Motte Chemical Company or by the Beckman pH Meter orPotentiometer.

Thirdly, ionized air is introduced into the flotation bath consisting ofeither positive or negative ions and indicated by'the pH value of thebath. duced into the bath when the pH value is above 7.0 and negativeions when the pH value of the bath'is below 7.0.

' Fourtbly, flotation reagents and conditioners are introduced into thebath and consist of the types which give off heavy'negative or positiveions.

Fifthly, the ore consists ofboth negative and positive minerals, thatis, in the above example the negative minerals are chalcopyrite, galena,pyrite, quartz, calcite, and mica and the positive minerals are thecolloidal basic hydroxides,

' basic oxides and other oxidized ores.

and included in this class are hydroxides of aluminum, fe'rric, copperand others.

' magnetite and hematite. It is a mixture of sulfldes and non-sulfidescontaining fine grained Sixthly, the film of oil on the air-oil-globuleentity takes either a negative or positive electrical sign on itssurface according to the pH value of the flotation bath. That is, thefilm of oil is positive when the flotation bath is acidic or the film isnegative when the bath is alkaline.

Seventhly, conditioners introduced into the flotation bath have theimportant role of modifying the hydrogen ion concentration of said bathby giving off heavy negative or positive ions and exchanging their ionsfreely with minerals and reagents.

Eighthly, \the insoluble film which is formed on the surface of mineralsis due to the free exchange of ions between minerals and flotationreagents and conditioners, by adsorption.

Ninthly, the electrical charge on the surface of minerals-is modifiedbyintroducing ions into the flotation bath of direct current impulsesinterrupted for short intervals in combination with the other steps inthe process such as introducing ionized air, electrolytes and flotationremlnerals in suspension and containing minerals agents.

Positive ions from the air are intro-' The changes in the electricalsign on the surface of minerals due to the free exchange of ions areillustrated in the following example:

Electrical sign of the eifective ion In this example, the gold content,lead and silver sulfides and chalcopyrite are the minerals desirable. tofloat as a lead concentrate, while' pyrite sphalerite, quartz, calciteand mica are depressed. The zinc minerals are floated in a separate zinccell as zinc concentrates.

First, direct current imgulses oi. 220 volts and 1.5 amperes are introuced into the flotation bath to the immersed electrodes containedtherein for 3 seconds and then interru ted for three seconds. The objectoi! this s to cause positive colloidal basic hydroxides to be attractedtowards the negative electrodes to impede the free exchange of ionsbetween said colloids and siliceous materials and in this manner toavoid activating negative silica by adsorption. It is also for thepurpose of modifying the pH value of the bath, for accelerating therelease of the ions from reagents and conditioners, for attractingnegative colloids towards positive electrodes, for the return of some ofthe reagents to their original status and structure after interruptionof current impulses, and in the present case to assist in making theflotation bath alkaline so ghlt its hydrogen ion concentration isPositive Secondlv, the negative minerals are chalcorpy'ite and galena.The electrical sign of the effective ion is Thirdly the kind ofconditioners introduced into the flotation bath are neutral tochalcogyrite and galena but depress pyrite and sp alerite. Theseconditioners for exam! ple are zinc sulphate (1.90 lbs. per ton) andsodium cyanide (0.3 lb. per ton. The electrical sign of the effectiveion is Fourthly, the conditioner which gives ofl positive ions is sodaash (1.0 lb. per ton or this ore) by exchanging them freely with galenaand chalcopyrite. The electrical sign of the eifective ion is Fifthly,the negative reagent introduced into the flotation bath which furnishesnegative ions is potassium xanthate (0.06 lb. er ton of ore). Itexchanges ions treel w th the minerals to form the insoluble Im on theirsurfaces by adsorbtion. The electrical sign of the effective ion isSixthly, positive ions from ionized air are introduced into theflotation bath for wetting purposes, that is, so that the film andmineral is surrounded by air and is water repellent. The electrical signof of the effective ion is Seventhly, the frother cresylic acid (0.04lb.

per ton) furnishes the negative ions for the film of oil surrounding theair-oil-globule entity. The electrical sign of the efiective ion iEighthly, positive ions introduced into the bath from the air completesthe process for flotation of the mineral-and-film entit and theair-oil-globule entity. The electr call sign of the effective ion is Inthe above example the flotation bath was alkaline due to theintroduction of direct current impulses interrupted for short intervalstogether with positive conditioners. The reagents used were of thenegative type, the ions from the air were of the positive type, theconditioners furnished positive ions and the mineralspresent that werefloated were of the negative type. The positive colloids were detainedin the pulp and the negative suspensoids were flocculated.

If the order of the positive and negative electrical signs of theeffective ions were interchanged in the example as illustrated, thenflotation of the minerals would not be economically improved. Forexample, if negative ions from the air were introduced into theflotation bath instead of positive ions, or if the pulp was acidicinstead of alkaline, or if the minerals were of the positive typeinstead of negative, or if direct current impulses were suspended,-then, the process would not be economically improved.

The direct current impulses interrupted for Negative Neutral PositiveNegative Positive Negative Positive "short intervals in combination withthe other steps in the process when introduced into the flotation bathfunction in the general scheme of the process by accelerating therelease 01' the effective ions of the reagents and conditioners, byfurnishing desirable additional ions to the pulp to modify the pH valueof the flotation bath, by attracting positive colloidal basic hydroxidestowards the negative electrodes which are completely immersed therein toprevent said colloids from adsorbing siliceous materials, by attractingnegative and positive colloidal suspensions towards positive andnegative electrodes to flocculate them respectively by neutralizingdispersed particles, by precipitating depressed minerals and removingthem together with colloidal basic hydroxides and film-forming mineralsfrom the bath, by allowing some reagents to return to their originalstatus and structure for further use in a continuous cycle ofbeneficiation, by removing undesirable suspensoids after neutralizationof charge. on their surfaces to avoid adsorption of desirable minerals,and by providing for a new arrangement of molecular structure for someof the reagents and minerals with their changed electrical sign andcharge of improved flotation purposes.

Table 1 Shows the results of introducing into a flotation bath directcurrent impulses to electrodes completely immersed therein of adequatevoltage and am rage to furnish desirable additional ions to said bathinterrupts ioiintervals of not less than one second and introducing intothe bath ionized air, flotation reagents. conditioners and emulsifiersfor activation or depression of minerals contained therein.

The pH value of the flotation bath is 8.2.

Table 2 Shows results after introducin into a fl ti ionized air,flotation reagents an ota on bath emulsifiers in unds per ton the sameas per Table No. 1, but without ntroducing into said bath direct currentim ulses to immersed electrodes interrupted for short ingervals as perTable No. 1.

f Assays per ton Product Weight Au Ag Pb Zn Cu Fe Pcr- Pcr- Pc- PPercent Ounces Ounce! cent cent on; refit Calc.head 100.00 004 19. 5.706.50 0.80 5.60 Lead cone. 13.00 0.28 131.49 35.00 8.34 3.02 2.36 Zincconc.. 16.00 0.014 7.112 5.06 32.24 1.60 16.93 Tails 71.00 0002 1.080.48 0.37 0.048 3.635

Distributionpercent The pH value of the flotation bath is 7.5."

Reagents and conditioners used in Tables No. 1

and No. 2

Reagents used 3332:; Rougher Cleaner 383g: Rouglier Cleaner ggg 331it'ifiid 3% o nm a gods 881186 h m 1.00

r a sfi n a 0.15 Pot.xanthatc 0.06 A. CY. R9. NO. 242 0.04 A. CY. R8.N0. 238 0.04

umnlmfn Cresylic acid.- 0.04 Amyl xanthate. 0.04

Re No. 242 is neutralized Aerofloat Flotation Reagefig sglgpl i ysig gyg$3.85 Sold by A Cy Co Re. No. 238 is a dry Aerofloat Flotation Reagent oThe tails in the weight percent column of Table No. 1 shows that silicaand calcite (negative minerals) are higher in content than in Table No.2, proving that direct current impulses interrupted for intervals notless than one second materially aid in depressing undesirable mineralsas well as fiocculating negative mineral suspensoids. Likewise, it showsthat the percentage of undesirable dispersed particles which have beendepressed after neutralization increases.

Table No. 1 shows that ironand aluminum basic oxides and colloidal basichydroxides are higher in content in the tails than in Table No. 2,indicating that direct current impulses flowing to the electrodesimmersed in the flotation bath attract said minerals towards theelectrodes and assist in reducing adsorption and activation of siliceousmaterials by said colloidal basic hydroxides.

Table No. 1 shows an improvement in the percent extraction of flotationof gold, silver, lead and copper in the lead concentrate and zinc in thezinc concentrate proving that it is an improved differentlal method forflotation of these minerals.

The tails of Table No. 2 show an increase in percentage of colloidswhich are floated with the zinc concentrates over the results in TableNo. 1, indicating that direct current impulses interrupted for shortintervals improves the grade 01 zinc concentrate.

Table No. 1 shows improved higher values for gold, silver, lead andcopper in the lead concentrates than in Table No. 2 indicating thatundeor to metathesis, or to anchored ions or to chemical reactionsbetween metal ions from oxidized surfaces and organic acid radicals ofthe collecting agents.

The tables prove that the steps in the process to obtain these resultscontribute to modify the pH value of the flotation bath, (Table No. 1shows a pH value 8.2 and Table No. 2 shows a pH value 7.5), andobviously changes the electrical sign and potential of the air-oil-bubblentity and the mineral-and-film entity.

The ions furnished by zinc sulphate and sodium cyanide are neutral togalena and chalcopyrite but depress sphalerite andpyrite. The ionsfurnished by soda ash are positive and serve to condition the lead andcopper minerals but oil film on the air-oil-globule entity. The ionsfurnished by sodium oleate are positive and activate oxides of minerals.

sirable film-forming minerals are detained from forming films ondesirable minerals in the bath v and also, restrain film-formingminerals from depressing desirable minerals.

The results of Table No. 1 show a decided improvement in extraction andgrade of minerals over the results in Table No. 2 and this difference isassigned to the novel steps in the combination process. These resultsindicate that The introduction into the flotation bath of direct currentimpulses of 220 volts and 1.5 amperes interrupted for short intervals of3 secondsv accelerated the release of dissociated ions of flotationreagents and conditioners in said bath, modified the hydrogen ionconcentration of the bath and furnished positive and negative ions tothe bath.

Positive ions from the air were introduced into the flotation bathbecause said bath was predetermined as alkaline.

The mineral content of the bath furnished both negative and positiveions.

The final charge and sign of the ions on the surface of themineral-and-fllm entity and the colloidal basic hydroxides (ironhydroxides) are restrained from activating undesirable minerals such assilica; that film-forming minerals (aluminum oxides) are restrained fromdepressing desirable minerals such as the sulfides of silver, lead,copper and zinc; that basic iron oxides (hematite) are removed from thebath before they form films with the oleates on negative minerals suchas on calcite and silica; that negative and positive suspensoids as wellas the reagents,

conditioners and emulsifiers modify the pH value of the bath, andfinally, it illustrates that the electrical sign and potential on thesurface ofminerals is modified by the films formed on said final chargeand sign on the air-oil-bubble entity determined the status of themineral for activaelectrodes contained therein in adequate voltage andamperage to electrolyse the solution or to supply desirable additionalions, or for the purpose of orienting or grouping minerals, or to attract colloids, basic hydroxides or magnetizable minerals whether due toelectrostatic charges, minerals towards the electrodes, or .tofiocculate,

to any ore under all destabilize or precipitate minerals, or finally, tomodify the pH value of the flotation bath.

If the pH value of the bath is found to be less than 7.0 or to beacidic, then negative ions from the air are introduced into the bath.The oil fllm surrounding the air-oil-globule has a positive electricalsign and the film of air for wetting purposes surrounding themineral-and-film entity has a negative electrical sign. .At this pointindicated by a mark X for convenience there are two,

conditions presented, that is, whether it is desirable to float negativeor positive minerals.

Case I If it is elected to float positive minerals, then continuing withthe process from X, I introduce positive reagents into the flotationbath, then negative conditioners. .The desirable mineral has a positiveelectrical sign. A summary of Case I is as follows:

1. Positive minerals are floated from the flotation bath. v

2. Negative conditionersv ar introduced to modify the pH value'of thepulp.

3.- Positive reagents are introduced to furnish positive ions and forforming the insoluble fllm on the surface of minerals with itselectrical sign.

4. Negative ions from the air are introduced for wetting purposes, thatis. to make the mineral-and-film water repellent.

5. Positive oil fllms are furnished by the frotherand for the fllm onair-oil-globules.

6. Negative ions from'the air are introduced to complete the process forforming the air-oilglobule and mineral-and-film entities with theirelectrical signs and charges for flotation of minerals.

The pH value of the flotation bath is below 7.0 and acidic.

The voltage and amperage of the direct current impulses interrupted forshort intervals is adequate to dissociate the molecules of the solutionin the bath or is introduced into the pulp to accelerate the release ofions from reagents or to modify the pH value of the flotation bath, orto furnish desirable additional ions to the bath, or to attract negativeor positive suspensoids towards positive or negative electrodesrespectively.

Case I! If it is desirable to use negative reagents in the above Case IIinstead of positive reagents, then it will be necessary to use positiveconditioners, while the remaining steps in the process are as follows;that is, I introduce into the pulp negative ions from the air, positiveconditioners and negative reagents for positive minerals.

The pH value of the flotation bath is below 7.0 and acidic.

The direct current impulses are introduced into the bath for similarreasons as indicated in Case I.

Case III If it is elected to float negative minerals instead of positiveminerals, then continuing with the process from the mark X, I introducepositive reagents into the flotation bath to form the insoluble film onthe surface of minerals. The desirable mineral has a negative electricalsign.

Under this example, when the bath is acidic or its pH value is below 7.0and direct current impulses have been introduced into the flotation bathand interrupted forintervals of not less than one second, the followingsummary exists:

1. Negative minerals are floated from the flotation bath.

2. Positive reagents furnish the positive electrical sign and forforming the insoluble fllm on the surface of the minerals.

3. Negative ions from the air are for wetting purposes. I

4. Positive oil films are furnished by the frother and for the air-oil-globules.

5. Negative ions from the air are introduced to complete the process forforming the air-oilglobules entity and the mineral-and-fllm entity.

The pH value of the flotation bath is below 7.0 and acidic.

continuing with the process from the point surfaces. I introducepositive conditioners to The voltage and amperage of the direct currentimpulses interrupted for short intervals is adequate to dissociate themolecules of the solution in the bath or is introduced into the pulp toaccelerate the release ofions of reagents or to modify the pH value ofthe flotation bath, or

to furnish desirable additional ions'to the bath, or to attractnegativeor positive suspensoids towards positive or negative electrodesrespectively.

Case IV If it is desirable to use negative reagents instead ofpositivereagents as in Case III then the conditioners introduced intothe bath must be of the type which furnish large positive ions while allof the remainingsteps in the process are as follows, i. e;, I introduceinto the pulp positive conditioners, negative reagents and negative ionsfrom the air, for negative minerals.v

The pH value of. the bath is found to be be-.- low 7.0 and acidic.

The direct current impulses are introduced into the bath for similarreasons as indicated for Case III.

Case V If the pH value of the pulp is found to be greater than 7.0 or tobe alkaline I introduce positive ions from the air into the flotationbath.

The oil fllm surrounding the air-oil-globule is.

negative and the film of the air for Fwetting purposes on the insolublefllm-and-mineral is positive.

At this point marked X for convenience there are two conditions toconsider that is, whether it is desirable to float negative or positiveminerals.

If it is elected to float negative minerals then,

marked X, I introduce into the flotation bath negative reagents to forminsoluble films on their exchange ions freely with desirable mineralsbut less so with undesirable minerals. Lastly, the desirable minerals tofloat have a negative electrical s gn.

Under this example when the bath is alkaline and direct current impulsesare introduced into the bath and interrupted for intervals of not lessthan one second, the following conditions exist:

1. Negative minerals are floated from the flotation bath.

2. Positive conditioners exchange ions freely with some of the mineralsfor conditioning purposes.

3. Negative reagents furnish negative ions freely with desirableminerals and for forming the insoluble film on the surface of minerals.

4. Positive ions from the air are introduced for wetting" purposes.

5. Negative oil films are furnished by frother and for the fllm on theair-oil-globules.

6. Positive ions from the air are introduced into the bath to completethe Process.

' The pH value of the pulp is above 7.0 or alkaline.

The voltage and the amperage of the direct current impulses interruptedfor short intervals is adequate to dissociate the molecules of thesolution in the bath, or is introduced into the pulp to accelerate therelease of ions of reagents or to modify the pH value of the flotationbath, or to furnish desirable additional ions to the bath, or to attractnegative or positive suspensoids towards positive or negative electrodesrespectively.

Case VI If it is desirable to use positive reagents instead of negativereagents as in Case V then, the conditioners introduced into the bathmust be of the type which furnish large negative ions while all of theother conditions of Case V are similar, that is, I introduce into thepulp negative conditioners, positive reagents and positive ions from theair for negative minerals.

Case v11 If it is elected to float positive minerals then continuingwith the process from X, I introduce negatisve reagents into theflotation bath to exchange ions freely with desirable minerals and toform insoluble films on their surfaces. Finally, the desirable mineralto float has a negative electrical sign.

Under this example when the bath is alkaline and direct current impulsesare introduced to the bath and interrupted for intervals ofnot less thanone second, the following conditions exist: 1. Positive minerals arefloated from the flotation bath.

2. Negative reagents furnish negative ions freely to exchange with saidminerals and for forming insolublefllmson the surface of positiveminerals.

3. Positive ions, from the air are introduced for wetting" purposes.

4. Negative oil films are furnished by frothers and for the fllm on theair-oil-globule entity.

5. Positive ions from the air are introduced into the bath to completethe process for form- 9 The voltage and amperage of the directcurrentimpulses interrupted for short intervals is adequate to dissociatemolecules of the solution is, I introduce into the pulp positivereagents, negative conditioners and positive ions from the air forpositive minerals.

. The pH value of the pulp is above 7.0 or alkaline. 1

The direct current impulses are introduced into the bath for similarreasons as indicated for Case VII.

The conditioners and reagents introduced into the flotation bath shouldbe of such a nature that they are qualified to exchange ions freely withsaid minerals but not necessarily in the same manner with all minerals.Therefore, it is possible to depress some minerals while activatingothers in the same bath. The process is found to be applicable to anyore whether it is of the sulfide or non-sulfide type. The free exchangeof ions of positive and negative minerals, positive and negative ions ofelectrolytes, emulsifiers and reagents, the positive and negative ionsfrom ionized air released by the introduction of direct current impulsesinterrupted for intervals for not less than one second for modifying thehydrogen ion concentration of the flotation bath, are the steps in theprocess by which the broad concept and adaptability of the process toany class of ore is clearly indicated.

in the bath, or is introduced into the pulp to accelerate the release ofions of reagents or to modify the pH value of the flotation bath, or tofurnish desirable additional ions to the bath, or to attract negative orpositive suspensoids towards positive or negative electrodesrespectively.

Case VIII If it is desirable to use positive reagents instead ofnegative reagents as in Case'VII then the conditioners introduced intothe bath must If the above procedure as outlined is not closely adheredto, then, flotation results will not be improved.

The eight cases cited show the acidity and alkalinity of the flotationbath and indicate at once what the electrical sign is on the surface ofthe oil-film of the air-oi'l-entity. They also indicate whether tointroduce negative or positive ions from the air into the bath. That is,if

the pulp is acid introduce negative ions from the.

air and if alkaline introduce positive ions from the air into said bath.The positive and negative reagents and conditioners introduced into thebath give off positive and negative ions which can be'interchanged ascited. If the steps which the process consists of are not followed asset forth in these eight cases and direct current impulses are suspendedfrom being introduced into the bath, then, flotation of the mineralswill not be improved.

I claim:

1. A froth flotation process for minerals which comprises subjecting apulp of the ore to be separated to agitation and aeration in thepresence of a collector for the desired mineral and intermittentlypassing a unidirectional electric current through the bath below thesurface, the intervals of the current flow and intervals between currentflow being substantially 1 to 3 seconds duration.

2. The process as claimed in claim 1 in which aeration isaccomplishedwith ionized 'air.

3. A froth flotation process as called for in claim 1 wherein the oretreated includes siliceous minerals and colloidal basic hydrorddes.

4. A froth process as claimed in claim 1 in which the ore containsnegatively charged minerals and positively charged colloids andsuspensoids, and wherein the aeration is accomplished with ionized air,whereby the exchange of ions between the minerals and colloids isprevented.

E. H. HOAG.

